A ventilation or check valve of this type is discussed in DE 19 38 206 A which forms the generic type, and is, for example, a constituent part of an electropneumatic ABS pressure control valve according to DE 197 01 200 C2 from the applicant of the present patent application. According to the embodiment which is shown there in FIG. 5, the ventilation or check valve is arranged in a lower ventilation opening of the housing of the ABS pressure control valve which serves to hold or lower the brake pressure of a slip-controlled pneumatic brake system of a vehicle in a manner which is dependent on brake slip. In order to lower the pressure in the case of excessive brake slip which is detected by an ABS electronic system, a control valve of the ABS pressure control valve is excited, as a result of which compressed air passes out of the brake line via the interior of the ABS pressure control valve into the ventilation opening and into the ventilation or check valve, the diaphragm lifting up from the valve seat as a result of the pressure gradient and it being possible for the compressed air to pass to atmosphere.
Furthermore, DE 10 2007 054 760 B3 discusses a ventilation or check valve of this type which is arranged there in a ventilation opening of a pressure relief valve of a compressed air brake system of a rail vehicle, in order to limit excessive pressure in a main air line to a predefined value during a filling stroke by virtue of the fact that excessive compressed air flows away via the ventilation opening and the ventilation or check valve arranged therein.
Patent document WO 96/21589 A1 refers to an application, in which a ventilation or check valve is arranged in a wall of a spring chamber of a spring accumulator brake cylinder, which spring chamber accommodates an accumulator spring, in order to ventilate the spring chamber in the case of a reduction in volume of said spring chamber brought about by release of the spring accumulator brake.
A common feature of all of said applications of a ventilation or check valve is that they are intended to permit the flow of a medium, for example of compressed air, only in one direction and to prevent it in the opposite direction. For the abovementioned applications, this means, for example, that the ventilation or check valve is intended to permit the flow of compressed air only from the interior of the relevant compressed air device to atmosphere, but is intended to prevent a flow in the opposite direction.
In addition to this basic function, ventilation or check valves which are used in the field of automotive technology and are configured as diaphragm valves of the generic type are intended to ensure a high air throughput, low throttling effects during the outflow, reliable blocking of the undesired flow direction, reliable prevention of the penetration of dirt, a low opening or response pressure and, above all, low noise development.
The latter has proven difficult, however, since high noise development is to be observed, above all, in the case of relatively compliant material of the diaphragm because the compliant diaphragm can then be excited more readily by the air flow to perform oscillations (solid-borne sound) which cause corresponding air-borne sound. If, in contrast, the rigidity of the material of the diaphragm is relatively high, the seal properties with respect to the valve seat tend to be moderate.